U.S. patent application number 13/911609 was filed with the patent office on 2014-12-11 for perpendicular magnetization with oxide interface.
The applicant listed for this patent is International Business Machines Corporation. Invention is credited to Guohan Hu, Daniel Worledge.
Application Number | 20140363701 13/911609 |
Document ID | / |
Family ID | 52005684 |
Filed Date | 2014-12-11 |
United States Patent
Application |
20140363701 |
Kind Code |
A1 |
Hu; Guohan ; et al. |
December 11, 2014 |
PERPENDICULAR MAGNETIZATION WITH OXIDE INTERFACE
Abstract
A mechanism is provided for a structure with perpendicular
magnetic anisotropy. A bottom oxide layer is disposed, and a
magnetic layer is disposed adjacent to the bottom oxide layer. The
magnetic layer includes iron and is magnetized perpendicularly to a
plane of the magnetic layer. A top oxide layer is disposed adjacent
to the magnetic layer.
Inventors: |
Hu; Guohan; (Yorktown
Heights, NY) ; Worledge; Daniel; (Yorktown Heights,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
International Business Machines Corporation |
Armonk |
NY |
US |
|
|
Family ID: |
52005684 |
Appl. No.: |
13/911609 |
Filed: |
June 6, 2013 |
Current U.S.
Class: |
428/832 |
Current CPC
Class: |
H01L 43/12 20130101;
H01F 10/329 20130101; H01L 43/08 20130101; H01F 10/3259 20130101;
G11B 5/8404 20130101; G11C 11/161 20130101; H01F 10/3286 20130101;
G11C 11/16 20130101; G11B 5/62 20130101 |
Class at
Publication: |
428/832 |
International
Class: |
G11B 5/62 20060101
G11B005/62 |
Claims
1. A structure with perpendicular magnetic anisotropy, comprising:
a bottom oxide layer; a magnetic layer disposed on top of the
bottom oxide layer, wherein the magnetic layer includes iron and is
magnetized perpendicularly to a longitudinal plane of the magnetic
layer; and a top oxide layer disposed on top of the magnetic
layer.
2. The structure of claim 1, wherein the bottom oxide layer is
MgO.
3. The structure of claim 1, wherein the bottom oxide layer
includes at least one of MgO, AlOx, HfOx, TiOx, TaOx, CuOx, VOx,
RuOx, SiOx, WOx, BOx, CaOx, ScOx, ZnOx, CrOx, MnOx, and
combinations thereof.
4. The structure of claim 1, wherein the top oxide layer is
MgO.
5. The structure of claim 1, wherein the top oxide layer includes
at least one of MgO, AlOx, HfOx, TiOx, TaOx, CuOx, VOx, RuOx, SiOx,
WOx, BOx, CaOx, ScOx, ZnOx, CrOx, MnOx, and combinations
thereof.
6. The structure of claim 1, wherein the magnetic layer is
CoFeB.
7. The structure of claim 1, wherein the magnetic layer includes at
least one of Fe, CoFe, CoFeB, CoFeBTa, and combinations
thereof.
8. The structure of claim 1, wherein a free layer in a spin torque
MRAM is formed by the bottom oxide layer, the magnetic layer, and
the top oxide layer.
9. The structure of claim 1, wherein a reference layer or part of
the reference layer in a spin torque MRAM is formed by the bottom
oxide layer, the magnetic layer, and the top oxide layer.
10. The structure of claim 1, wherein a disk in a hard disk drive
is formed by deposition of the bottom oxide layer, the magnetic
layer, and the top oxide layer.
11-20. (canceled)
Description
BACKGROUND
[0001] The present invention relates generally to magnetic memory
and magnetic storage devices, and more specifically, to materials
in and configurations for a device with perpendicular
magnetization.
[0002] Spin transfer torque is an effect in which the orientation
of a magnetic layer in a magnetic tunnel junction or spin valve can
be modified using a spin-polarized current. Charge carriers (such
as electrons) have a property known as spin which is a small
quantity of angular momentum intrinsic to the carrier. An
electrical current is generally unpolarized (consisting of 50%
spin-up and 50% spin-down electrons). A spin polarized current is
one with more electrons of either spin. By passing a current
through a thick magnetic layer, one can produce a spin-polarized
current. If a spin-polarized current is directed into a magnetic
layer, angular momentum can be transferred to the magnetic layer,
changing its magnetic orientation. This can be used to flip the
orientation of the magnet.
SUMMARY
[0003] According to an exemplary embodiment, a structure with
perpendicular magnetic anisotropy is provided. The structure
includes a bottom oxide layer, and a magnetic layer adjacent to the
bottom oxide layer. The magnetic layer includes iron and is
magnetized perpendicularly to a plane of the magnetic layer. A top
oxide layer is adjacent to the magnetic layer.
[0004] According to another exemplary embodiment, a method of
forming a structure with perpendicular magnetic anisotropy is
provided. The method includes depositing a bottom oxide layer, and
depositing a magnetic layer adjacent to the bottom oxide layer. The
magnetic layer includes iron and is magnetized perpendicularly to a
plane of the magnetic layer. A top oxide layer is deposited
adjacent to the magnetic layer.
[0005] Additional features and advantages are realized through the
techniques of the present invention. Other embodiments and aspects
of the invention are described in detail herein and are considered
a part of the claimed invention. For a better understanding of the
invention with the advantages and the features, refer to the
description and to the drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0006] The subject matter which is regarded as the invention is
particularly pointed out and distinctly claimed in the claims at
the conclusion of the specification. The forgoing and other
features, and advantages of the invention are apparent from the
following detailed description taken in conjunction with the
accompanying drawings in which:
[0007] FIG. 1A illustrates a cross-sectional view of a three layer
device with perpendicular magnetic anisotropy according to an
embodiment.
[0008] FIG. 1B illustrates a graph of the perpendicular magnetic
field and a graph of the in-plane magnetic field according to an
embodiment.
[0009] FIG. 2A illustrates a cross-sectional view of a spin torque
transfer random access memory (STT-RAM) device according to an
embodiment.
[0010] FIG. 2B illustrates an example of the STT-RAM device in
which the free magnetic layer is implemented with the three layer
device according to an embodiment.
[0011] FIG. 2C illustrates an example of the STT-RAM device in
which the reference magnetic layer is implemented with the three
layer device according to an embodiment.
[0012] FIG. 2D illustrates an example of the STT-RAM device in
which the free magnetic layer and reference magnetic layer are
respectively implemented with separate three layer devices
according to an embodiment.
[0013] FIG. 3 illustrates a hard disk drive (HDD) with the three
layer device according to an embodiment.
[0014] FIG. 4 illustrates a method for forming a three layer
structure device with perpendicular magnetic anisotropy according
to an embodiment.
DETAILED DESCRIPTION
[0015] An embodiment discloses a device with perpendicular
magnetization that may be utilized in various applications.
[0016] Dense spin torque MRAM requires magnetic layers with
magnetization perpendicular to the plane with large magnetic
anisotropy, and compatible with MgO to give high magnetoresistance.
State of the art work has shown that Ta|CoFeB|MgO satisfies these
requirements.
[0017] However, the anisotropy may not be large enough to make
devices for the 20 nanometer node size and below. Also, magnetic
layers with magnetization perpendicular to the plane with large
magnetic anisotropy would also be useful for hard disk drive
storage media.
[0018] Magnetic anisotropy is the directional dependence of a
material's magnetic properties. In the absence of an applied
magnetic field, a magnetically isotropic material has no
preferential direction for its magnetic moment, while a
magnetically anisotropic material will align its moment with one of
the easy axes (as discussed herein perpendicular magnetic
anisotropy (PMA) is aligned perpendicularly). An easy axis is an
energetically favorable direction of spontaneous magnetization that
is determined by the sources of magnetic anisotropy.
[0019] Embodiments disclose structures that have high perpendicular
magnetic anisotropy energy density. Perpendicular magnetic
anisotropy energy density refers to the product of free layer
saturation magnetization M.sub.s, free layer thickness t, and
perpendicular anisotropy field H.sub.k.
[0020] Now turning to the figures, FIG. 1 illustrates a
cross-sectional view of a three layer device 100 with perpendicular
magnetic anisotropy according to an embodiment. The device 100
includes a magnetic layer 110 containing iron (Fe), sandwiched in
between a top oxide layer 105 and a bottom oxide layer 115. As
understood by one skilled in the art, the oxide layers contain
oxygen.
[0021] In the device 100, the Fe--O bonds on both interfaces 150
and 160 to produce very large perpendicular magnetic anisotropy
(i.e., vertical magnetization in device 100). In other words, the
iron of the magnetic layer 110 bonds with the oxygen in the top
oxide layer 105 at interface 150 and the iron of the magnetic layer
110 bonds with the oxygen in the bottom oxide layer 115 at
interface 160 to produce the large perpendicular magnetic
anisotropy for the device 100. The device 100 provides a simple
perpendicular material system with large perpendicular magnetic
anisotropy that can be utilized in various applications as
discussed further herein. As compared to CoFeB layers with a single
oxide interface, the M.sub.stH.sub.k of samples with double oxide
interfaces can be improved by 5.times. or more. FIG. 1B shows one
example of such a structure where the bottom oxide layer is MgO and
top oxide layer is MgTiOx. In this particular sample, the
M.sub.stH.sub.k product is .about.1.1 ergs/cm.sup.2, compared to
.about.0.2 erg/cm.sup.2 for a typical MgO|CoFeB|Ta sample.
[0022] In FIG. 1B, a chart 170 shows the magnetic perpendicular
field (i.e., vertical) strength (in Oersteds (Oe)) on the
horizontal axis and shows the moment (M.sub.st in emu/cm.sup.2) on
the vertical axis for the structure, where EMU is the
electromagnetic unit. The line 172 shows the measured magnetic
moment when a perpendicular magnetic field is applied which
traverses from a positive magnetic field (e.g., +800 Oe) to
negative magnetic field (e.g., -800 Oe). Line 174 shows the
measured magnetic moment when the perpendicular magnetic field is
applied which traverse from a negative magnetic field (e.g., -800
Oe) to positive magnetic field (e.g., +800 Oe). In chart 170, the
saturation moment (when the perpendicular magnetic field is
applied) is denoted by 176.
[0023] In FIG. 1B, a chart 180 shows the magnetic in-plane field
(i.e., horizontal) strength (in kilo Oersteds (kOe)) on the
horizontal axis and shows the moment (M.sub.st in emu/cm.sup.2) on
the vertical axis for the structure. The line 182 shows the
measured magnetic moment when the in-plane magnetic field is
applied which traverses from a positive magnetic field (e.g., +15
kOe) to negative magnetic field (e.g., -15 kOe). Line 184 shows the
measured magnetic moment when the in-plane magnetic field is
applied which traverse from a negative magnetic field (e.g., -15
kOe) to positive magnetic field (e.g., +15 kOe). In chart 180, the
saturation in-plane magnetic field is denoted by 186 and the value
is H.sub.k=10 kOe.
[0024] M.sub.s is the saturation magnetization of the free layer
material, t is the thickness of the free layer, and H.sub.k is the
perpendicular anisotropy field of the free layer. The
M.sub.stH.sub.k product is referred to as energy density. For a
given device size, the higher the M.sub.stH.sub.k product, the
higher the thermal activation energy barrier which translates to
better retention. Perpendicular magnetic anisotropy energy density
refers to the product of free layer saturation magnetization
M.sub.s, free layer thickness t, and perpendicular anisotropy field
H.sub.k.
[0025] The device 100 is compatible with MgO for high
magnetoresistance if one of the oxide layers 105 and/or 115 is
MgO.
[0026] The device 100 can be formed as discussed below. The bottom
oxide layer 115 is grown first, and then the Fe-containing magnetic
layer 110 is grown on top of the bottom oxide layer 115. Next, the
top oxide layer 105 is grown on top of the magnetic layer 110.
[0027] The top oxide layer 105 may include MgO, AlO.sub.x,
HfO.sub.x, TiO.sub.x, TaO.sub.x, CuO.sub.x, VO.sub.x, RuO.sub.x,
SiO.sub.x, WO.sub.x, BO.sub.x, CaO.sub.x, ScO.sub.x, ZnO.sub.x,
CrO.sub.x, MnO.sub.x and/or any other oxide, including combinations
of oxides, mulitcomponent oxides, and multilayered oxides. Also,
the bottom oxide layer 115 may include MgO, AlO.sub.x, HfO.sub.x,
TiO.sub.x, TaO.sub.x, CuO.sub.x, VO.sub.x, RuO.sub.x, SiO.sub.x,
WO.sub.x, BO.sub.x, CaO.sub.x, ScO.sub.x, ZnO.sub.x, CrO.sub.x,
MnO.sub.x, and/or any other oxide, including combinations of
oxides, mulitcomponent oxides, and multilayered oxides. The "x"
subscript is a variable that represents the number of atoms of the
oxygen element (to form the oxide), which can apply to any varied
number of atoms suitable for the compound of an oxide as understood
by one skilled in the art.
[0028] The Fe-containing magnetic layer 110 may include Fe, CoFe,
CoFeB, CoFeBTa, and/or any other Fe-containing magnetic layer,
including combinations of magnetic materials, magnetic alloys, and
multilayered magnetic materials, as long as the materials (of the
magnetic layer 110) at the interfaces 150 and 160 with the oxides
contain Fe. A particular embodiment is MgO|CoFeB|MgO, where the
bottom oxide layer 115 is MgO, the magnetic layer 110 is CoFeB, and
the top oxide layer 105 is MgO.
[0029] The Fe-containing magnetic layer 110 may be 10-50 angstroms
(.ANG.) thick. The top oxide layer 105 may be 2-20 angstroms thick.
The bottom oxide layer 115 may be 2-20 angstroms thick.
[0030] The device 100 may be utilized in a spin torque MRAM device
(as the free layer, and/or reference layers (or part of the
reference layers)), as the media in hard disk drives, and/or in any
other application where a perpendicularly magnetized structure is
needed.
[0031] There are various applications for the device 100, and a few
examples are discussed in FIGS. 2A, 2B, 2C, and 2D (generally
referred to as FIG. 2). FIG. 2A illustrates a cross-sectional view
of a spin torque transfer random access memory (STT-RAM) device 200
according to an embodiment. The device 100 may replace a reference
magnetic layer 20, part of a reference magnetic layer 20, and/or a
free magnetic layer 40 in the STT-RAM device 200. The device
structure of the STT-RAM device 100 includes a magnetic tunnel
junction (MTJ) 70. The magnetic tunnel junction 70 has a reference
magnetic layer 20, a tunnel barrier 30 on the reference magnetic
layer 20, and a free magnetic layer 40 on the tunnel barrier 30.
The reference magnetic layer 20 is on a seed layer 10. The seed
layer 10 may be one or more different materials (depending on the
exact reference magnetic layer 20) to grow the reference magnetic
layer 20. A cap layer 50 is disposed on top of the free magnetic
layer 40. The reference magnetic layer 20 and the free magnetic
layer 40 sandwich the tunnel barrier 30 in between. The tunnel
barrier 30 is a thin insulator (typically a few nanometers
thick).
[0032] The free magnetic layer 40 is shown with double arrows to
illustrate that spin torque current (or spin polarized current) via
voltage source 75 can flip the magnetic orientation of the free
magnetic layer 40 to up or down as desired. The reference magnetic
layer 20 is shown with an up arrow to illustrate a magnetic
orientation in the up direction.
[0033] To write the STT-RAM device 100, the voltage source 75
applies voltage such that a spin torque current may flip the
magnetic orientation of the free magnetic layer 40 as desired. When
the magnetic orientations of the free magnetic layer 40 and the
reference magnetic layer 20 are parallel (i.e., pointing in the
same direction), the resistance of the MTJ 70 is low (e.g.,
representing logic 0). When the magnetic orientations of the free
magnetic layer 40 and the reference magnetic layer 20 are
antiparallel (i.e., pointing in opposite directions), the
resistance of the MTJ 70 is high (e.g., representing a logic
1).
[0034] FIG. 2B illustrates an example of the STT-RAM device 200 in
which the free magnetic layer 40 is implemented (or replaced) with
the device 100 according to an embodiment. The device 100 can also
implement the tunnel barrier 30 or vice versa as seen below.
[0035] In FIG. 2B, the device 200 includes the layers 10, 20, 30,
40, and 50. The free magnetic layer 40 now includes the bottom
oxide layer 115, the magnetic layer 110 with iron, and the top
oxide layer 105 (of device 100). In this case, the bottom oxide
layer 115 is disposed directly on the reference layer 20, and the
bottom oxide layer 115 acts as the tunnel barrier 30. The cap layer
50 is disposed on the top oxide layer 105. As such, the device 100
with its perpendicular magnetization is utilized as the free
magnetic layer 40. Operating as the free magnetic layer 40, the
device 100 can have an upward pointing magnetization or a downward
pointing magnetization based on applying voltage of the voltage
source 75 to generate spin current as understood by one skilled in
the art.
[0036] As another example of utilizing the device 100 for its
perpendicular magnetic anisotropy, FIG. 2C illustrates an example
of the STT-RAM device 200 in which the reference magnetic layer 20
is implemented (or replaced, or partly replaced) with the device
100 according to an embodiment. Note that part of the device 100
may implement the tunnel barrier 30 or vice versa.
[0037] In FIG. 2C, the device 200 includes the layers 10, 20, 30,
40, and 50. The reference magnetic layer 20 now includes the bottom
oxide layer 115, the magnetic layer 110 with iron, and the top
oxide layer 105 (of device 100). The bottom oxide layer 115 is
disposed on the seed layer 10, and the free magnetic layer 40 is
disposed on the top oxide layer 105 (wherein the top oxide layer
105 acts as the tunnel barrier layer 30) of the device 100.
Accordingly, the device 100 with its perpendicular magnetization is
utilized as the reference magnetic layer 20. Operating as the
reference magnetic layer 20, the device 100 may have a downward
pointing magnetization that provides a reference layer to the free
magnetic layer 40.
[0038] FIG. 2D illustrates an example of the STT-RAM device 200 in
which both the free magnetic layer 40 and the reference magnetic
layer 20 (or part of the reference magnetic layer) are respectively
implemented (or replaced) with the devices 100 according to an
embodiment. In this case, the reference layer 20 and the free layer
40 are sharing an oxide layer. When referring to the reference
layer 20, the shared oxide layer is referred to as top oxide layer
105a (which may be the same as top oxide layer 105). When referring
to the free magnetic layer 40, the shared oxide layer is referred
to as bottom oxide layer 115a (which may be the same as bottom
oxide layer 115).
[0039] In FIG. 2D, the reference magnetic layer 20 or part of the
reference layer 20 is formed by the bottom oxide layer 115, the
magnetic layer 110a with iron, and the top oxide layer 105a (of
device 100). The bottom oxide layer 115 is disposed on the seed
layer 10, and the top oxide layer 105a acts as the tunnel barrier
30. Accordingly, the device 100 with its perpendicular
magnetization is utilized as the reference magnetic layer 20 to
provide a reference layer to the free magnetic layer 40 (e.g.,
during reading).
[0040] Also, in FIG. 2D, the free magnetic layer 40 includes the
same bottom oxide layer 115a (acting as the tunnel barrier 30), the
magnetic layer 110b with iron, and the top oxide layer 105 (of
device 100). The cap layer 50 is then disposed on the top oxide
layer 105. As such, a separate device 100 with its perpendicular
magnetization is also utilized as is the free magnetic layer 40.
Note that the magnetic layers 110a and 110b are the same material
of the magnetic layer 110.
[0041] Note that although FIGS. 2A through 2D shows the free
magnetic layer 40 above the reference magnetic layer 20, the
location of the free magnetic layer 40 and the reference magnetic
layer 20 can be interchanged such that the free magnetic layer 40
is below the reference magnetic layer 20. In this case, the free
magnetic layer 40 would be located in the previous location of the
reference magnetic layer 20, and likewise the reference magnetic
layer 20 would be located in the previous location of the free
magnetic layer 40.
[0042] Another example of utilizing the perpendicular magnetic
anisotropy device 100 is discussed in FIG. 3. FIG. 3 illustrates a
hard disk drive (HDD) 300 with the perpendicular magnetic
anisotropy device 100 (magnetic recording media) according to an
embodiment. A hard disk drive is a data storage device used for
storing and retrieving digital information using rapidly rotating
disks (platters) coated with magnetic material.
[0043] The HDD 300 includes a disk/platter 305. One or more of the
devices 100 are deposited to cover the disk/platter 305. In the
sandwiched structure discussed above, the device 100 includes the
bottom oxide layer 115, the Fe magnetic layer 110 adjacent to the
bottom oxide layer 115, and the top oxide layer 105 adjacent to
magnetic layer 110. Note that the individual layers 105, 110, and
115 are not repeated in FIG. 3 for the sake of conciseness but are
understood to be part of the device 100.
[0044] The HDD 300 retains its data even when powered off. Data is
read in a random-access manner, which means individual blocks of
data can be stored or retrieved in any order rather than just
sequentially. The HDD has one or more rigid ("hard") rapidly
rotating disks (platters) 300 with magnetic heads 310 arranged on a
moving actuator arm 315 to read and write data to the device 100.
As shown in FIG. 3, the magnetic head 310 reads and writes to the
device 100 by applying a magnetic field to flip the magnetic
orientation of the device 100 (e.g., upward or downward pointing
magnetic orientation). Further details of reading and writing with
a hard disk drive are not discussed but are understood by one
skilled in the art.
[0045] FIG. 4 illustrates a method 400 for forming a three layer
structure device 100 with perpendicular magnetic anisotropy
according to an embodiment. Reference can be made to FIGS. 1, 2,
and 3.
[0046] The bottom oxide layer 115 is deposited at block 405, and
the magnetic layer 110 is deposited on top of and adjacent to the
bottom oxide layer 115. The magnetic layer 110 includes iron and is
magnetized perpendicularly to the longitudinal plane of the
magnetic layer 110 (and the device 100). Note that the longitudinal
plane of the magnetic layer 110 is the lengthwise direction (i.e.,
horizontal direction) from left to right (of vice versa) in the
cross-sectional views of FIGS. 1A, 2B, 2C, and 2D, while the
perpendicular direction is vertical (e.g., up and down or vice
versa).
[0047] The top oxide layer 105 is deposited on top of and adjacent
to the magnetic layer 110 at block 415 to form the perpendicular
magnetic anisotropy device 100.
[0048] The bottom oxide layer 115 may be MgO. Also, the bottom
oxide layer includes at least one of MgO, AlOx, HfOx, TiOx, TaOx,
CuOx, VOx, RuOx, SiOx, WOx, BOx, CaOx, ScOx, ZnOx, CrOx, MnOx, and
combinations thereof.
[0049] The top oxide layer 105 may be MgO. Additionally, the top
oxide layer 105 includes at least one of MgO, AlOx, HfOx, TiOx,
TaOx, CuOx, VOx, RuOx, SiOx, WOx, BOx, CaOx, ScOx, ZnOx, CrOx,
MnOx, and combinations thereof.
[0050] The magnetic layer 110 may be CoFeB. Further, the magnetic
layer includes at least one of CoFe, CoFeB, CoFeBTa, and
combinations thereof.
[0051] With reference to FIG. 2, a free magnetic layer 40 in a spin
torque MRAM device 200 may be formed by the bottom oxide layer 115,
the Fe containing magnetic layer 110, and the top oxide layer 105
of device 100. Also, a reference magnetic layer 20 in a spin torque
MRAM device 200 may be formed by the bottom oxide layer 115, the Fe
containing magnetic layer 110, and the top oxide layer 105 of
device 100.
[0052] With reference to FIG. 3, a disk/patter 305 in a hard disk
drive 300 is formed by deposition of the bottom oxide layer 115,
the magnetic layer 110, and the top oxide layer 105 (to be the
storage media for reading and writing).
[0053] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one or more other features, integers,
steps, operations, element components, and/or groups thereof.
[0054] The corresponding structures, materials, acts, and
equivalents of all means or step plus function elements in the
claims below are intended to include any structure, material, or
act for performing the function in combination with other claimed
elements as specifically claimed. The description of the present
invention has been presented for purposes of illustration and
description, but is not intended to be exhaustive or limited to the
invention in the form disclosed. Many modifications and variations
will be apparent to those of ordinary skill in the art without
departing from the scope and spirit of the invention. The
embodiment was chosen and described in order to best explain the
principles of the invention and the practical application, and to
enable others of ordinary skill in the art to understand the
invention for various embodiments with various modifications as are
suited to the particular use contemplated.
[0055] The diagrams depicted herein are just one example. There may
be many variations to this diagram or the steps (or operations)
described therein without departing from the spirit of the
invention. For instance, the steps may be performed in a differing
order or steps may be added, deleted or modified. All of these
variations are considered a part of the claimed invention.
[0056] While the preferred embodiment to the invention had been
described, it will be understood that those skilled in the art,
both now and in the future, may make various improvements and
enhancements which fall within the scope of the claims which
follow. These claims should be construed to maintain the proper
protection for the invention first described.
* * * * *